A water company has been fined £ 146,000 after it's polluted about a mile (1.6km) from a brook with sewage.
The Environment Agency found ammonia levels in Grendon Brook, Northants were toxic to aquatic life.
Leicester Magistrates 'Court found a lack of maintenance at Anglican Water's Yardley Hastings' sewage plant in August 2016.
The Agency's Adam Glassford said the company "did not live up to their environmental responsibilities".
He said: "It's our job as a regulator to protect people and wildlife, and we will take action when they're put at risk."
Tests carried out by ammonia were more important than ever before – enough to be extremely toxic to aquatic life.
The pollution was caused by various failures at the pumping station, which should be alerted to the problem.
The spill was reported on August 24, but was not acted on, and the company said the report was made, the Agency said.
The pollution continues intermittently for two days until 26 August.
The Agency acknowledged that it was Anglian Water which reported the incident, and there was no evidence of any dead fish or invertebrates.
Anglian Water Admission, Environmental Permitting Regulations and the Water Resources Act, and also had to pay $ 10,676 in costs.
The company has gone through the steps to fix the faults and clean up the brook.